Rapid Changes in Arctic and Antarctic Ice: A Review of the Past Decade

Arctic sea ice and Antarctic ice shelves have undergone a rapid retreat in the past decade, responding to a scale and pace of climate warming that is unprecedented within the past few millennia. Beginning in 2002, summer sea ice extent in the Arctic has reached a series of new record lows, culminating in 2007, when September mean sea ice extent was just 50% of what it was in the 1950s. The retreats are caused by warm ocean and air advection into the Arctic, and progressive loss of old, thick Arctic sea ice as a result of increased summer melting. In the Antarctic Peninsula, a series of ice shelves (thick ice floating plates derived from glacial flow off the continent) have disintegrated, most spectacularly in 2002 (Larsen B ice shelf) and 2008 (Wilkins Ice Shelf). These events are a response to increased air temperature and summer melting. Marine geological evidence from the seabed below the former shelves and other observations suggest that these areas had previously been stable for 400 to 12,000 years. Dramatic increases in glacier flow (by 2 to 8-fold) are observed after the ice shelf losses. The expected trends for the future in the Arctic and Antarctic suggest: an ice-free Arctic in summer within two or three decades, with a resulting major impact on Northern Hemisphere climate; and a potential doubling in the rate of sea level rise from increased Antarctic (and Greenland) ice flow.